Readers: If you want to build the module featured in this post, please go to PCBWAY's Community pages--gerbers ready to download and/or fabricate as well as KiCAD files, PDF's, BOM etc., are here.
Also please visit PCBWAY's site using the link here--it will help this blog. Thanks.
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Back again....from the previous post I switched from Eagle to Kicad for schematic capture and gerber file creation.
To put KiCAD EDA to the test I laid out and fabricated a Eurorack synthesizer module I know pretty well: Rene Schmidt's "Fastest ADSR in the West".
Good news, the KiCAD based design, in Euro format, was easy to lay out, easy to troubleshoot and rework, and overall, works great. Success!
Posts about the last time I built the ReneDSR (in PAIA's Frac format) are here and here.
I originally laid this post's project with a lot of through hole resistors and whatnot, a 3 board design, but the highly skilled Elton from Otter Mods challenged me to use more SMD. So you will see a lot of 1206 SMD parts in this build as well.
Build photo time:
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| Happiness is new PCB's from this blog's patient sponsor, PCBWAY. |
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| Two boards: main and front panel. Main board combines hardware and mostly SMD parts to allow the "skiff ready" 6HP footprint. |
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| Testing as I go--the ICs are drawing correct amounts of current and not heating up. |
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| Testing.... |
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| Oh Calcutta! Seems working. |
SMD ADVANTAGES
Being afraid of my own shadow I set my bench up for SMD but continued to use through hole for most projects.
KiCADSR uses through hole (or "THT" as Kicad calls it) components here and there, for instance, the 555 timer IC.
Why? I didn't have SMD 555's in my junk box.
Otherwise, for this new KiCAD era it was time to stop being wimpy about THT.
Here's the thinking:
I don't need a microscope for everything SMD. I have bad eyesight but could work with 1206 sized parts, for the most part, wearing only reading glasses.
SMD Parts turned out to be easier to swap after initial fabrication. Really? Yes. I soldered a 220ohm resistor between the voltage rails instead of 100K. Needless to say this was not a good idea and the part heated up quickly.
Replacing a THT resistor in this kinda situation wouldn't have been impossible but may not have been easy either. I could have lifted a trace for instance. With SMD it was easy! I heated up the part's pads quickly with my iron--each in succession--then lifted it out with tweezers; cleaned up the pads with wick and soldered the new part. I also experimented using my rework tool for this. No, all the parts on the board didn't melt off. No, I didn't make a huge mess. I found both processes quicker and easier than using a solder sucker to remove THT parts.
I didn't need as much room to store parts. I have a whole wall of bins for THT parts, but only a few small boxes for SMD. At some point SMD makes more sense in this regard as my psychiatrist wife (no longer my psychiatrist girlfriend--update, we got married, she is so wonderful, and I got very, very lucky) can't give up endless domestic space to my puzzling hobby.
I could put annoying .1uF filter caps on the back side of the PCB to save space. In fact, I could have distributed parts on both sides, not just filter caps.
For the KiCADSR I put one .1uF cap on the board's backside, then wondered why I didn't put all the filter caps on the back side. So if you build this, make sure to flip the main PCB and solder on that part.
In general I found I could fit a lot more circuitry in a smaller space with SMD, and too damn much of Eurorack is all about everything being really tiny.
Redoing incorrect traces is easier when using SMD. This one was hard to believe. I had 3 fixes necessary to get KiCADSR to work: I missed a trace during schematic capture and 2 of the pins on the 3.5mm jacks were swapped. Quickly fixed. To wit:
FIXES
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| Three--count 'em--THREE fixes were needed. To my surprise: not too hard to solder these fixes in with SMD |
Elton was right, kludging fixes with SMD was easier than I thought: I prepped and tinned some 22 gauge wire and soldered it to the butts of the appropriate components. I thought this was going to suck but at the end of the day was it easy. Note: the project I posted at PCBWAY community (here) already has the fixes and the symbol library at github (here) has the updated parts. I have tested this updated PCB working.
OUTTRO
KiCAD is vastly superior to Eagle, and SMD is superior in many ways to THT. It's taken me years of being told this to finally take it to heart, but maybe now I have.
Too often I am too set in my ways to move on--until I actually move on--and only then realize I should have moved on a long time ago. Is there a lesson in here somewhere? Yes, but I will almost certainly continue to ignore it.
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